This paper questions the assumption made in classic Optimality Theory (Prince & Smolensky 1993 [2004]) that markedness constraints are an innate part of Universal Grammar. Instead, we argue that constraints are acquired on the basis of the language data to which L1 learning children are exposed. This is argued both on general grounds (innateness is an assumption that should not be invoked lightly) and on the basis of empirical evidence. We investigate this issue for six general markedness constraints in French, and show that all constraints could be acquired on the basis of the ambient data. Second, we show that the order of acquisition of the marked structures matches the frequency of violations of the relevant constraints in the input quite well. This argues in favour of a phonological model in which constraints are acquired, not innate, i.e. a model in which grammatical notions such as constraints are derived from language use.